farmer



(No Model.) 7

M. G. FARMER.

p ELECTRIC LAMP. No. 265,790. Patented Oct. 10, 1882..

UNITED STATES PATENT OFFICE.

MOSES G. FARMER, OF NEWPORT, R. I., ASSIGNOR TO THE UNITED STATES ELECTRIC LIGHTING COMPANY, OF NEW YORK, N. Y.

ELECTRlC LAMP.

SPECIFICATION forming part of Letters Patent No. 265,790, dated October 10, 1882.

Application filed March 7, 1881. (No model.)

sections are composed of some suitable refrac tory metal offering a resistance much greater in proportion to its length than the remainder of the circuit, and which becomes incandescent in consequence of such resistance upon the passage of the current, and thereby pro duces light.

My invention consists in an improved construction of the light-producing portion of the electric lamp, by which the illumination may be rendered uniform over a comparatively large surface or may be concentrated at a single point.

In the acconi 'ianying drawings, Figure l is a perspective view of my improved lamp, and Fig. 2 represents a detail view of the illuminator or light-giving portion of the lam p.

4 If a bar, wire, or strip of platinum, iridium, or other similar refractory metal be rendered incandescent by the passage of an electric current through it, a mild and pleasant light is emitted, much less concentrated and glaring than the light obtained from an are between carbon pencils, and ofamuch more uniform character, provided the electric current is maintaiued at a constant strength. Platinum affords a light equivalent to about one hundred candles per square inch of incandescent surface when within 220 of its temperature of fusion, whileiridium, from its higher meltingpoint, produces a still greater proportionate amount of light than platinum under the same conditions. In accordance with this principle I construct my lamp by taking a bar or strip of one of the hereinbefore-mentioned metals,

preferably a fiat strip, as shown at L in Fig. 1, the thickness of which may be about onetenth or Iess of its greatest bread th. This is atlixed in an upright position between two metallic standards, p and p, by means otsuitable clamps, 12 and 19 These standards are secured to a base, B, of any suitable non-eonducting material by, means of screwsff or otherwise. A lever-switch, S, provided with an insulating knob or handle, serves to close or open the branch of the circuit passing through the lamp when it is desired to turn the light on or oil? I sometimes-prefer to use a ditt'erent arrangement, known as the pegswitch, iuwhich the circuit is completed by inserting a slightly-conical metallic plug between two metallic bars insulated from each other.

In Fig. 2 I have shown the configuration ot' the metallic strip which constitutes the illuminator of the lamp. The curves of the edges of the strip in Fig. 2 are formed by a geometrical line in conformity with the ascertained law of the conduction of heat in the particular metal employed, so as to obtain a uniform temperature throughout the whole length of the strip, and consequently a uniform illumi natingpower from the entire surface. A portion of the heat generated in the strip bythe passage of the current is conducted away by the clamps or holders at each end, which tends to reduce the temperature of the strip at any given point in proportion to-the nearness of that point to the holder. By making the strip of the form shownin Fig. 2 this reduction of temperature at any given point is compensated by the generation ot'a greater amount of heat at that point consequent upon the increased resistance encountered by the electric current in proportion to the reduction in the sectional area of the conductor.

I claim as my invention-- 1. An electric lamp the"light-producing por tion of which consists of a thin and broad strip of metal having its edges shaped to a geometrical curve corresponding with the law of heat conductivity in such metal, so as to produce a uniform illumination throughout every portion In testimony whereof I have hereunto suh- 10 of saidlstrip, substantially as and for the purscribed my name this 3d day of March A. D. pose specified. 1881.

2. An electric lamp the light-giving portion of which is composed of a flat strip of metal MOSES G. FARMEB. broadest in the center of its length, and grad ually decreasing in breadth from the center to WVitnesses: each end thereof, substantially as and for the SARAH J. FARMER, purpose specified. I DARIUS BAKER. 

